I recommend you get a couple of price quotes based on a design that you like. The range for the cost of a remodel for a bathroom is large.
Per the National Association of Realtors (NAR) Annual Remodeling Survey for the Pacific region as of January, 2011, a mid-range remodel costs $19,000 and an upper end remodel costs $66,000. It depends greatly upon what you choose for materials and workmanship. This means, for you, your costs will be somewhere in that range.
On the mid-range remodel, a seller recoups about 80% of his investment and on a high end remodel, a seller recoups about 63%. The NAR Research did not specifiy, but this is most likely for master bathrooms.
The commonly accepted range for a average house main bathroom update is $4000 to $5000.
There is a large difference between remodeling and updating. If you'd like, I am happy to meet with you to discuss what would be appropriate for a Madison Park home, or I can send you the Remodel Research document to which I am referring.
Remodeling changes walls and ceiling structures, whereas updating is simply updating the finishing from tubs, to sinks to counters, cabinets and countertops.
Bathrooms are not usually about "square footage" as the cost is plumbing and fixtures and not room size. So it depends on whether it is a 5 piece master bath, a full bath (usually a hall bath) or a 3/4 bath in a basement with a cheap one piece corner shower. It also depends on if you are rearranging the fixtures in any way or adding a fixture...which is usually not the case.
Tile work can be very expensive vs a one piece tub wall surround and a vinyl floor. The cost of bathrooms is more about the what than the size. If it's not a master bathroom, the cost is usually about $5,000 give or take for everything new including the window and medium vs cheapest quality. But you may have to shop around a bit to get that price for an average sized full hall bathroom. A 3/4 bath in a basement is usually cheaper and a Master Bath more costly.
Ballparking the cost of a Master Bath remodel is like trying to Ballpark a kitchen remodel. Often a huge variance in cost. I'll assume it's a standard, full hall bath from your question.
Here in Seattle Area a lot of people are having good luck finding reasonable contractors via Angie's List.